Many vehicles include an antenna used for wireless communication performed with, for example, a wireless communication base station. In order for a vehicle to maintain a satisfactory communication state while traveling where the communication environment constantly changes, there is a demand for an in-vehicle antenna that has an improved function for maintaining communication such as a high-gain antenna. Patent document 1 describes one example of an in-vehicle antenna that has an improved function for maintaining communication.
The in-vehicle antenna described in patent document 1 includes a first antenna and a second antenna that are spaced apart from each other in a front-rear direction of a vehicle. The element length of the first antenna is less than the element length of the second antenna. Thus, the first antenna acts as a director of the second antenna, and the second antenna obtains a satisfactory directionality at the front of the vehicle. Additionally, the second antenna acts as a reflector of the first antenna. The first antenna also obtains a satisfactory directionality at the front of the vehicle.